Load your Shield with 147s as they lose less velocity from the short barrel plus they hit harder.
A fella clocked the 115s, 124s, 124 +Ps and 147s out of a 4" barrel and recorded 'em. Then he did the same with the 3" barrel and wrote the difference in percentage of loses. The 147s came out with less percentage of loses than the others.
Also the +P didn't really add the velocity too much to the short barrel. Most of the propellant is wasted after the bullet left the barrel but the muzzle blast was cool though.
EDIT: Test the 147s in your gun first before carry.